Tangential thought:
Imagine a developing sentient species that originated & lives on the far side of the Moon.
As their spheroid rotates, they’d see the universe swirling by, and over time deduce that they revolve around the Sun. They may observe other planets, and work out the concept of a sun-centric solar system. This goes on for a very long time.
Then one day, an intrepid explorer takes an unusually long journey. As he (it?) travels, an incredibly bright & noisy (in the electromagnetic spectrum) orb rises over the horizon. Imagine the shock of discovering that your planetary body is in permanent orbit around a larger & populated body just light-minutes away ... and you’re the first of your sentient species to discover it.
That’s what led to the war which wiped out the moon civilization. Not even the atmosphere survived.